Semiconductor edge-emitting lasers are currently used in a variety of technologies and applications, including communications networks. Generally, edge-emitting lasers produce a stream of coherent, monochromatic light by stimulating photon emission from a solid-state material. Example edge-emitting lasers commonly used as optical transmitters include Fabry-Perot (“FP”) lasers and distributed feedback (“DFB”) lasers. Edge-emitting lasers can be employed as optical transmitters to convert electrical signals into optical signals for transmission via an optical communication network.
As part of the manufacturing process of edge-emitting lasers, multiple edge-emitting laser diodes are generally formed on a single wafer. After the wafer processing is completed, individual rectangularly shaped edge-emitting lasers must be separated from the wafer. Individual edge-emitting lasers can be separated from the wafer by mechanically scribing the wafer with a precision instrument and then cleaving the wafer at each scribe location using a cleaving blade.
One cleaved side of each rectangularly shaped edge-emitting laser generally serves as the output facet. The output facet is the surface of the edge-emitting laser from which the light produced by the laser is emitted. In order to achieve reliable laser emissions, the output facet of an edge-emitting laser must be substantially free from damage and contamination after the cleaving process.
One common defect in edge-emitting laser output facets is metallic contamination. Metallic contamination occurs when a portion of a top metallic contact layer of an edge-emitting laser, composed of gold for example, is inadvertently deposited on the output facet of the laser or one or more adjacent lasers during the cleaving process. Examples of ridge waveguide (“RWG”) edge-emitting lasers 50 with gold contamination 52 on an output facet 54 are shown in FIGS. 1A-1D.
Other common defects in edge-emitting laser output facets are microstep defects. Microstep defects are mechanical defects in the output facet of an edge-emitting laser that are caused by excessive cleaving force being applied to the laser during the cleaving process. An example of a ridge waveguide edge-emitting laser 60 with a microstep defect 62 on an output facet 64 is shown in FIG. 2.
Current processes for cleaving edge-emitting lasers often result in a high percentage of unusable lasers due to defects, such as metallic contamination and microstep defects, in the facets of the lasers.